1. Field of Invention
The invention relates to a mainboard and a power control device and, in particular, to a mainboard, which includes a chip having a plurality of input power sources, and a power control device thereof.
2. Related Art
Accompanying with the progress of technologies, various kinds of electrical information devices, such as computers, mobile phones, network servers, etc., must employ several chips to enable themselves for matching the modern information life. Thus, it is one of the most important researches in the information industry to make the chips work normally.
In general, the chips are installed on a circuit board, such as a printed circuit board. To achieve the objectives of increasing the integration of chips, decreasing the power consumption, and enhancing the operation speed, the core circuits of the chips usually have the lower bias voltage and electrical signals with the lower voltage level. However, the chips also include some other circuits, such as the I/O buffer, which need higher voltage levels. For example, the mainboard usually includes a south bridge chip, which includes a plurality of digital logics. The digital logics may be driven by the voltage level of 3.3 volts or 2.5 volts. Accordingly, the mainboard must configure two power rails, including, for example, a 3.3-Volt power rail and a 2.5-Volt power rail. The power rails connect to the south bridge chip for providing the voltages of different voltage levels, which allow the south chip operating normally.
Ideally, the two power rails reach the regulating voltage states at the same time, so as to drive the digital logics of the south bridge chip simultaneously. However, the two power rails usually can not reach the regulating voltage states (2.5 volts and 3.3 volts) at the same time. If the time delays that the two power rails reach the regulating voltage states are too long, the chip may operate abnormally.
Therefore, this invention provides a mainboard and a power control device thereof, which can shorten the time delays that the two power rails reach the regulating voltage states.